In a packet-based network line, heavy traffic is sometimes concentrated so that an increase occurs in packet discards and packet delays. The services that do not particularly take measures against packet discards and delays are called best-effort services. For example, the Internet is one of the examples of these services. On the other hand, bandwidth-guaranteed services that guarantees packet transfer up to a certain bandwidth are provided. In bandwidth-guaranteed services, the bandwidth contracted by a certain customer, who is a user, is a basically fixed bandwidth.
On the other hand, there is an idea of bandwidth on-demand services. In bandwidth on-demand services, a bandwidth is reserved and guaranteed for a certain period of time. For example, a bandwidth on-demand service is suitable for the case of using the bandwidth only for a few hours at night for taking a backup.
As an example of related art, Japanese Laid-open Patent Publication No. 2001-282760 is known.